Duplicating



Patented Jan. 20, 1931 UNITED STATES PATENT OFFICE DUPLICATING No Drawing. Application filed June 5, 1926, Serial No. 114,020, and in Germany February 27, 1926.

\ l0 fixed alkali, or a carbonate thereof or a salt having an alkaline reaction. Ammoniacal inks are unsatisfactory on.account of the volatility of the ammonia. Inks containing a fixed alkali or an alkaline salt react only very slowly with the preparation on the plate, whilst if the sensitivity of the plate is enhanced, for instance, by the addition of a sulpho-cyano compound, there is the danger that the white portions will become tinted on account of the high sensitivity. By the present invention, the origin'al'to be duplicated is prepared by means of an ink or colour containing hexamet-hylene-tet-ramine. Satisfactory results are thereby obtained inasmuch as on the one hand, the reaction between the ink of the original and the preparation on the plate is exceedingly sensltive, whilst on the other hand,'the stais practically unlimited on account 0 the non-volatility of hexamethylene-tetrauiine. Instead of hexamethylene-tetramine, a salt thereof maybe used.

In particular, the invention permits the ouring ribbon or pad for use in connection with uphcatingLprocesses, a problem which has hitherto not been solved in a manner free from objection. If, for example, hexarnethylene-tetramine is added to one of the 'usual preparations for impregnating the ribbon or pad, for instance in a proportion amounting to per cent of the pre aration, the typescript roducedwith the aid of the impregnated'ri bon reacts with suflicient'rability of the ink or writing in the original.

production of a satisfactory inking or 001- adhesive ink, or by producing typescript with the aid of a ribbon or pad containing a viscous or adhesive substance, and then -dusting over the original so prepared a powinvention and the best means. I know of carrying the same into practical eflect, I claim 1. In a duplicating process of the kind described herein, the step for forming the-characters of the original with a material containing hexemethylene-tetramine.

2. In a duplicating process of the kind described herein, the step which comprises forming the original with an ink containing heXamethylene-tetramine.

3. In a duplicating process of the kind described herein, the step which comprises adding hexamethylene-tetramine to the ink from which the original is prepared.

4. An ink, for ,the process referred to in claim 2, containing hexamethylene-tetramine.

5. An inking ribbon or pad, for the proc-' ess referred to in claim 1, lmpregnated with hexamethylene-tetramine. v

In. testimony whereof I have signed my name to this specification.

DR. LEO SILBERSTROM pidity and clearness with the preparation on the plate, without any treatment being necessary to increase the sensitivit of the latter.

The process may also be carried'out by preparing the original by means of a viscous b1 

